Improvement in mode of steaining wood-saws



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T0 VALL WHOM IT MAY CONOERN:

Be it known that I, Josnrn R. WEBSTER-of Boston, in the county of Suffolk, and State of Massachusetts,`

have invented an Improvement in Straining Saws; and I do hereby declare that the following, taken in connection with the drawings 'which ,accompany and form partof this specification, is a description of my invention sufficient toienable those skilled in the art to practise it The invention relates to the straining of saws, and more particularly to mechanism for straining the blades o f the common and-well-kno-wn wood-saws, in which the blade is hung in a square or quadrangular frame, one

4end-bar of which forms, orhas formed upon it, the handle for driving the sm Various devices have been designed, and are now more or less-in use, as -substitutes for the old method of straining thev blade by twisting a. doubled cord, connecting the upper ends of the two main bars of the frame, descriptions of somo of which devices may be found in United States VPatents Ncs.'25,015, 29,991, 30,073, 30,076, (reissue 1,452) 37,999, and 68,194. These devices are, all of them, more or less objectionable, either for want of simplicity, or on account of ineiliciency, or because too expensive.

In my inventionIheve sought to produce a mechanism or device for straining the blade, which, while being very simple and incxpensive,'sbould permit the saw tobe strained with the greatest facility,and to any desirable degree of tautness.

l My inventionconsists, primarily, in the employment, in co'nuection with a bow or frame of a hand-saw, of a lever connected at one end to the saw-frame bar, and hung upon or with relation to a fulcrum-pin in such manner that a. scr'ewvand nut operating uponthe opposite end of the lever, causes the lever either to operate directly upon the saw-'blade with relation' to one of the frame-bars, and thereby strain the blade, or to operate upon the frame-bar with relation to one of the braces, or 'vice versa, end thereby elfect the same object.

The draw ing represents, :it/A, a. side viewr of a common wood-sew and frame embodying my invention. B represents a. section taken on the line x fr. C and D are side and front views of the 4straining-lever. a and b denote the two en`dbars, c the centre-brace, d the saw-blade, and e the upper brace, the generalirelative disposition 'of these'parts Vbeing the same as in other frames. One end ofthe brace e is secured to the bar a by a pin,

while its opposite end slides freely through a mortise in the bar b; and on the inner side of one ot' the bnr-sat- 6,'(prei`erably the bar b, opposite tothe handle) andjust above the brace e, is a ringbolt,g, (or a staple,) into the eye of which the upper end, h, of a lever, z', hooks, as seen at A and B. t This lever (which isl formed subi stantially as seen at C and D) has a long mortise, 7c, made through it, by mea-ns of which the lever is slipped upon the upper brace, as seen at A and B, the lever resting, when applied, against n fulcrum-pin, l, inserted in and projected from the brace. Another mortise, m, (or an extension of the same mortise,) is made in the lower end of the lever, and through this a screw or screw-pin, u, projects, this pin being driven through the adjacent bar b, its head bearing upon the outer surface of said b ar. On the outer or threaded end of the screw-pin is s nut, o, which, in being screwed up on the screw, presses against the lever z', as will be readily understood by inspection of the drawiugst A. As the end of the lever is thus forced towards the barby the nut, its opposite end draws the upper part of the bar towards the fulcrum-pin, forcing the lower end of the bar outwards, and' thereby straining the saw-blade.

As the lever is loosely connected, both to the bar and to the brace e, it will be obvious that no relativev l strain comes upon the bar and brace, but that they move freely, both with respect to each other and to the lever. The straining-device may thus be applied to either bar a or b, or may be applied to the outer surface of either bnr, and a similar lever-mechanism may also be similarly applied with respect to the centre-brace, or even so as to operate directly upon the blade, but the specitic arrangement shown is considered the most desirable and .practical for wood-saws.

In applying the lever to bow-saws, and directly to or in connection with the blade of `common Wood-saws,

the lever is pivoted both to the end of the bow-bar and to the saw-blade, or works against pivots applied to each, this lever having, in such case, a neck, which is embraced by the frame, a fork below such neck, which straddles the blade, anda mortisc above the neck, made for the screw to work through.

Among the advantages of this method of straining saws may be mentioned the following Both ends of the brace e pass completely through both end-pieces a b of the saw-frame in all degrees of strain, thus preserving ,the frame, und is operated to strain the saw-blade, substantially as set fort-h.

its symmetry and giving to itv always a firm support. The brace c is not liable to be bent in the operation of straining the saw. By' combining the screw with the let'er, great As'tmining-pmver is obtained, the degree of strain may be finely adjusted und securely maintained, while the tension upon the-threads of the screw is only a part of the strain which is:A exerted upon the frame.

The lever may be mede Without the ul'ortise Iig-being, iu such cese, placed on one side of the bace; but it will. beobvious that s'uch arrangement is not so reliable ais-that in which the brace is carried dreetly'through thel'ever, as shown.

. I claim, in combination with a. hand-smv frame, the lever-z', and mechanism by which it is conhected with JOSEPH R. WEBSTER.

v l/litnesses:

FRANCIS GOULD, S. B. KIDDER. 

